1. Field of Invention
This invention relates to powered lawn mowers and external combustion powered lawn mowers in particular.
2. Description of Prior Art
Presently available engine powered lawn mowers are driven by internal combustion engines which are noisy, inefficient and highly polluting. Electrically driven lawn mowers are awkward to use and dangerous. Available external combustion engines are typically very slow starting because of both thermal and rotational inertia.
J. A. Connell U.S. Pat. No. (3,893,300) approximates a standard Brayton cycle with compression, constant pressure heating, and approximately isentropic expansion through a power producing expansion turbine. There is a thermal capacitance to help energize the turbine in response to rapid increases in the load. In contrast to our invention, Connell has adiabatic rather than isothermal or near isothermal expansion in a directly heated expander, as we teach, and lacks a supply of preheated air into the combustion chamber. There is no anticipation nor obviousness in Connell because of strong thermodynamic, functional and structural distinctions.
Van Don C. Brinkerhoff U.S. Pat. No. (4,224,798) teaches an engine driven compressor which is refrigerant cooled with an air motor. Compressed, but not heated, air is supplied to the internal combustion engine. There is no directly heated expansion, no regenerative heat exchanger and no preheated combustion air. Our invention is, therefore, both distinct and superior.
T. L. Cosby U.S. Pat. No. (4,663,939) teaches a modified Rankine cycle with superheating while our quiet lawn mower engine is a modified, open cycle Ericcson cycle. Cosby also lacks regenerative heat exchange and heated expansion. From the point of utility it can be shown that concurrent compression and cooling is not especially efficient. The First Law predicts that the work energy available for compression is depleted by simultaneous cooling. Secondly, electrolysis adds additional parasitic losses to the system. Thermodynamically, functionally and structurally our invention is clearly distinct from Cosby.